This application claims the benefit of Korean Patent Application No. 2002-779, filed on Jan. 7, 2002 in Korea, which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
The present invention relates to a liquid delivery system and more particularly, to a liquid delivery system having a safe unit that prevents a contamination of the liquid delivery system due to an inflow of ambient air when a power abruptly stops being supplied.
2. Discussion of the Related Art
Recently, various deposition methods of semiconductor devices, for example, a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method, are suggested according to a high integration and a high performance of semiconductor devices. Since characteristics of a thin film by the CVD method are largely dependent on a structure and a capability of a liquid delivery system, makers of semiconductor devices develop and use their own liquid delivery system.
FIG. 1 is a schematic view showing a structure of a related art chemical vapor deposition apparatus including a liquid delivery system. As shown in FIG. 1, a wafer xe2x80x9cWxe2x80x9d is loaded on a susceptor 40 by a robot arm (not shown) through an open portion (not shown) of a process chamber 20 from a load lock chamber (not shown) when a slit valve (not shown) is open. After the robot arm is taken out from the process chamber 20, the slit valve is closed and a main valve 52 is open. Thus, the process chamber 20 obtains a high vacuum state through a continuous pumping procedure of a main pump 50. When the high vacuum state is maintained in the process chamber 20, a liquid source material controlled by a mass flow controller (MFC) 14 and a delivery gas delivering the liquid source material are combined in a liquid delivery system 10 and injected onto the wafer xe2x80x9cWxe2x80x9d from a nozzle 30 at an upper portion of the process chamber 20 through an injection valve 12. When a depositing process is completed, the wafer xe2x80x9cWxe2x80x9d is taken out from the process chamber 20 by the robot arm. Even though the injection valve 12 is closed because no more liquid source materials are necessary, the mass flow controller 14 is continuously operated to keep a uniform flow of the liquid source material. Accordingly, the liquid source material flows out through an auxiliary valve 15 and an auxiliary pump 16.
When the injection valve 12 is open, the auxiliary valve 15 is closed and the liquid source material and the delivery gas flow only into the process chamber 20. Since the injection valve 12 is closed when a depositing process is completed, the auxiliary valve 15 is open and the liquid source material and the delivery gas are exhausted by the auxiliary pump 16, thereby a subsequent process prepared.
In the liquid delivery system, if an electric power stops being supplied during a preparation of a subsequent process, an exterior air can be reversely injected into and contaminate the liquid delivery system. To prevent this back stream and the contamination, the auxiliary valve 15 should be closed when the electric power stops being supplied.
FIG. 2 is a schematic diagram illustrating an operation of a related art safe unit of a liquid delivery system. As shown in FIG. 2, when a power stops being supplied due to an electricity failure, a first signal xe2x80x9cS1xe2x80x9d of stop of an auxiliary pump 16 (of FIG. 1) is applied to a Programmable Logic Controller (PLC). The PLC performs an interlock check and receives a second signal xe2x80x9cS2xe2x80x9d as a result of the check. The PLC analyzes the second signal xe2x80x9cS2xe2x80x9d and generates a third signal xe2x80x9cS3xe2x80x9d of closing an auxiliary valve 15 (of FIG. 1). The auxiliary valve 15 (of FIG. 1) is closed according to the third signal xe2x80x9cS3xe2x80x9d so that a contamination of a liquid delivery system due to a back stream can be prevented.
However, since the related art safe unit of a liquid delivery system performs the interlock check by a software method, it takes about 4 to about 6 seconds to generate the third signal xe2x80x9cS3xe2x80x9d and close the auxiliary valve 15 (of FIG. 1) according to the result of the check by a software method. The delay time of about 4 to about 6 seconds for the interlock check and the closing the auxiliary valve 15 (of FIG. 1) means that a lot of ambient air have been already injected into the liquid delivery system and the liquid delivery system is contaminated. Accordingly, the process should be stopped to replace the contaminated apparatus and this decrease the throughput. Moreover, the expense for replacement raises the production cost. When the auxiliary pump 16 (of FIG. 1) is out of order, the same problem occurs.
Accordingly, the present invention is directed to a safe unit of a liquid delivery system that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a liquid delivery system having a safe unit that prevents a contamination due to a back stream of exterior ambient air by using an element of hardware.
Another object of the present invention is to provide a liquid delivery system having a safe unit that has a simple structure and a low cost of maintenance.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid delivery system having safe unit includes: an injection valve connected to a chamber; a mass flow controller connected to the injection valve; an auxiliary valve connected between the injection valve and the mass flow controller; an auxiliary pump connected to the auxiliary valve; and a relay electrically connected to the auxiliary valve.
The mass flow controller adjusts a mass of a liquid source material and supplies the liquid source material into the chamber through the injection valve during a process in the chamber. A delivery gas is further supplied into the chamber through the injection valve with the liquid source material during a process in the chamber. The liquid source material is exhausted through the auxiliary valve by the auxiliary pump after the process in the chamber. The auxiliary valve is closed according to a first signal of the relay when the auxiliary pump is stopped.
The liquid delivery system further comprises a programmable logic controller electrically connected to the auxiliary pump and the relay. A second signal of stop of the auxiliary pump is applied to the programmable logic controller when the auxiliary pump is stopped and a third signal of operating the relay is generated at the programmable logic controller due to the second signal and applied to the relay.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.